Coupling process

ABSTRACT

An alkene selected from ethene, propene, and mixtures thereof is coupled with an aromatic hydrocarbon having an active hydrogen on a saturated alpha-carbon in the presence of a supported potassium or potassium alloy as a catalyst and cesium oxide as a co-catalyst. In a preferred embodiment of the invention, the active hydrogen-containing aromatic hydrocarbon is an alkylbenzene, such as toluene.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of copending application Ser.No. 276,531, filed Nov. 28, 1988, now abandoned

FIELD OF INVENTION

This invention relates to a process for coupling ethene and/or propenewith an aromatic hydrocarbon having an active hydrogen on a saturatedalpha-carbon.

BACKGROUND

As disclosed, e.g., in U.S. Pat. Nos. 3,244,758 (Eberhardt) and4,179,580 (Cobb) and in European Patent No.128001 (Kudoh et al.), it isknown that supported alkali metals, including potassium andsodium-potassium alloys, are useful as catalysts in the coupling ofethylenically-unsaturated hydrocarbons with aromatic hydrocarbons havingan active hydrogen on a saturated alpha-carbon. The supported alkalimetals are more effective than the corresponding unsupported alkalimetals in such reactions but are still not as effective as might bedesired.

Claff et al., Journal of Organic Chemistry, Vol. 20, pp. 20 440-442 and981-986 (1955) disclose the use of sodium oxide in the metalation oftoluene by potassium; and the speculative teachings of U. S. Pat. No.3,691,242 (Cheng et al.) include the substitution of an alkali metaloxide for an alkali metal alkoxide as a cc-catalyst in the alkalimetal-catalyzed reaction of cumene with ethylene or propylene.

Copending application Ser. No. 356,186 (Smith), filed May 24, 1989,discloses the use of an oxide of sodium, potassium, or rubidium as aco-catalyst for the coupling of ethene and/or propene with aromatichydrocarbons having an active hydrogen on a saturated α-carbon in thepresence of a supported alkali metal as a catalyst.

SUMMARY OF THE INVENTION

An object of this invention is to provide a novel process for couplingethene and/or propene with an aromatic hydrocarbon having an activehydrogen on a saturated alpha-carbon.

Another object is to provide such a process which utilizes a supportedalkali metal as a catalyst.

A further object is to provide such a process in which the reaction rateand product yield are increased.

These and other objects are attained by coupling ethene and/or propenewith an aromatic hydrocarbon having an active hydrogen on a saturatedalpha-carbon in the presence of a supported potassium or potassium alloyas a catalyst and cesium oxide as a co-catalyst, the catalystcomposition containing about 200-1500 weight % of support and about 4-40mol % of co-catalyst, based on the amount of alkali metal catalyst.

DETAILED DESCRIPTION

As already mentioned, the alkene which is coupled with the aromatichydrocarbon in the practice of the invention may be ethene, propene, ora mixture thereof. However, it is preferably propene or a propene-ethenemixture.

The aromatic hydrocarbon having an active hydrogen on a saturatedalpha-carbon may be any such compound that is known to be useful in suchreactions, such as toluene, ethylbenzene, n-propylbenzene,isopropylbenzene, n-butylbenzene, sec-butylbenzene, isobutylbenzene,n-eicosylbenzene, o-, m-, and p-xylenes, o-, m-, and p-ethyltoluenes,1,3,5-trimethylbenzene, 1,2,4,5- and 1,2,3,5-tetramethylbenzenes,p-diisopropylbenzene, 1- and 2-methylnaphthalenes, dimethylnaphthalenes,1-ethyl-4-n-octadecylnaphthalene, 1,4-di-n-pentylnaphthalene,1,2,3,4-tetrahydronaphthalene, indan, cyclohexylbenzene,methylcyclohexylbenzene, diphenylmethane, etc. However, it is generallya hydrocarbon corresponding to the formula RR'R"CH, in which R is anaryl group of up to 20 carbons and R' and R" are independently selectedfrom hydrogen and alkyl and aryl groups of up to 20 carbons; and it isapt preferably to be an alkylbenzene having one or more ar-alkyl groups.A particularly preferred aromatic hydrocarbon is toluene.

The mol ratio of alkene to aromatic hydrocarbon varies with theparticular reactants employed and the products desired, particularlysince the aromatic hydrocarbon may have one or more active hydrogens,and it may be desired to react the alkene with only one or with morethan one active hydrogen in the aromatic hydrocarbon. It is frequentlypreferred to employ the reactants in the stoichiometric amountsappropriate for the preparation of the desired product. However, eitherreactant can be used in excess.

The alkali metal employed as a catalyst may be potassium or a potassiumalloy, e.g., a sodium-potassium alloy having a potassium content of40-90% by weight. As in Cobb, the teachings of which are incorporatedherein in toto by reference, it appropriately has its surface areaincreased by being finely divided or liquid as well as by beingsupported on any suitable support material, such as diatomaceous earth,activated charcoal, granular coke, silica, alumina, pumice, porcelain,quartz, steel turnings, copper shot, sodium carbonate, potassiumcarbonate, etc. The amount of alkali metal used is a catalytic amount,generally about 2-10 mol %, based on the amount of either of thereactants when they are employed in equimolar amounts or on the amountof the major reactant when they are not utilized in equimolar amounts.

The co-catalyst of the invention is cesium oxide, which like the alkalimetal, is used in finely divided form.

The reaction is conducted by heating a mixture of the alkene, the activehydrogen-containing aromatic hydrocarbon, the supported catalyst, andthe co-catalyst under substantially anhydrous conditions at a suitabletemperature generally about 100°-300° C., preferably about 175°-200° C.,to couple the reactants. It is generally conducted in the absence of adiluent or in the presence of an excess of the activehydrogen-containing aromatic hydrocarbon as the sole diluent. However,an inert diluent can be used if desired. Exemplary of such diluents areliquid alkanes, cycloalkanes, and aromatic hydrocarbons, such aspentane, hexane, isooctane, cyclohexane, naphthalene,decahydronaphthalene, white oils, etc.

The process of the invention proceeds at a faster rate and provideshigher product yields with fewer by-products than comparable processesconducted in the absence of the co-catalyst, and it is particularlyadvantageous as a means of alkylating alkylaromatic compounds,especially alkylbenzenes, to form compounds useful as solvents, internalstandards, intermediates for polymers, pharmaceuticals, or pesticides,etc. It has the advantage over the Smith process of forming smalleramounts of methylpentene and tar-like by-products than the processutilizing an oxide of sodium, potassium, or rubidium as the co-catalyst.

The extent to which the use of both the support and the co-catalystincreases the activity of the potassium or potassium alloy catalyst issurprising. Comparison of experiments in which both the support and theco-catalyst were employed with experiments in which neither was used,experiments in which only the support was utilized, and experiments inwhich only the co-catalyst was utilized demonstrate that the support andco-catalyst act synergistically to provide an increase in catalyticactivity that is greater than the additive effect that might have beenexpected from the results achieved by the use of the supports andco-catalysts separately.

The following examples are given to illustrate the invention and are notintended as a limitation thereof.

COMPARATIVE EXAMPLE A

A suitable reaction vessel was charged with 92 g (1.0 mol) of toluene,C₁₁ paraffin as a GC standard, and 1.0 g of NaK (an alloy having a Kcontent of 78% by weight). The mixture was stirred and heated to 185° C.in 15 minutes, after which propene was charged until a pressure of 2758kPa was reached; and the propene pressure was then maintained at2689-2758 kPa throughout the reaction. Periodically the stirrer wasstopped to allow the solids to settle; and samples were drawn, allowedto cool to room temperature, and subjected to GC analysis to determinethe amounts of unreacted toluene, desired isobutylbenzene (IBB) product,and n-butylbenzene (NBB), methylindan (MI), and methylpentene (MP)by-products. Finally the reaction was stopped by cooling the reactor to75° C., venting most of the propene, and injecting 10 mL of methanolunder nitrogen pressure to quench the catalyst. The results of theanalyses are shown below.

    ______________________________________                                        Time    Mols × 100                                                      (min.)  Toluene     IBB    NBB     MI   MP                                    ______________________________________                                         40     100         0      0       0    0                                      80     91          1.8    0.2     0.01 0.2                                   160     83          9.6    1.0     0.2  0.9                                   240     70          17.2   1.6     0.5  1.4                                   ______________________________________                                    

COMPARATIVE EXAMPLE B

Comparative Example A was repeated except that 4.9 g of diatomaceousearth was included in the initial charge to the reaction vessel. Theanalytical results are shown below.

    ______________________________________                                        Time    Mols × 100                                                      (min.)  Toluene     IBB    NBB     MI   MP                                    ______________________________________                                         0      100         0      0       0    0                                      40     100         0      0       0    0                                      80     93.0        3.5    0.2     0.46 0.4                                   120     78.3        11.3   0.53    2.56 1.2                                   160     66.0        17.4   0.81    4.12 1.7                                   200     62.1        21.2   0.98    4.90 2.0                                   240     60.3        22.8   1.05    5.18 2.2                                   ______________________________________                                    

COMPARATIVE EXAMPLE C

Comparative Example A was repeated except that 8.5 mmol of -325 meshcesium oxide was included in the initial charge to the reaction vessel.The analytical results are shown below.

    ______________________________________                                        Time    Mols × 100                                                      (min.)  Toluene     IBB    NBB     MI   MP                                    ______________________________________                                         80     99          0.1    0       0    0                                     160     97          2.2    0.2     0.1  --                                    240     77          12.6   1.3     0.9  0.5                                   ______________________________________                                    

EXAMPLE I

Comparative Example A was repeated except that both 4.9 g ofdiatomaceous earth and 8.6 mmol of cesium oxide were included in theinitial charge to the reaction vessel. The analytical results are shownbelow.

    ______________________________________                                        Time    Mols × 100                                                      (min.)  Toluene     IBB    NBB     MI   MP                                    ______________________________________                                         0      100         0      0       0    0                                      40     --          2.0    0.24    0.07 0.2                                    80     86.4        14.0   1.53    0.85 1.04                                  120     66.3        31.6   3.25    1.76 2.3                                   170     49.8        44.6   4.49    2.16 2.8                                   200     41.6        49.8   4.97    2.22 2.9                                   240     36.3        52.2   5.19    2.25 2.9                                   ______________________________________                                    

The amount of tar-like by-products obtained after methanol hydrolysis ofthe catalyst and reactor residues was determined to be 1.15 g/g of NaKand 2.20 g/mol of IBB formed.

EXAMPLE II

Example I was essentially repeated except that the amount of cesiumoxide used was 4.3 mmol. The analytical results are shown below.

    ______________________________________                                        Time    Mols × 100                                                      (min.)  Toluene     IBB    NBB     MI   MP                                    ______________________________________                                         0      100         0      0       0    0                                      40     --          1.2    0.13    0.04 0.1                                    80     --          5.0    0.55    0.26 0.5                                   120     85.6        16.7   1.92    0.77 1.3                                   160     61.2        35.9   4.21    1.06 2.9                                   200     44.6        51.0   5.86    1.06 4.3                                   240     33.3        58.9   6.57    1.00 4.9                                   ______________________________________                                    

The amount of tar-like by-products obtained after methanol hydrolysis ofthe catalyst and reactor residues was determined to be 1.71 g/g of NaKand 2.90 g/mol of IBB formed.

As can be calculated from the % conversions of toluene after 240 minutesin the preceding examples, the activity of the catalyst was increased by32.3% by using a support in the absence of cesium oxide, decreased by23.3% by using cesium oxide in the absence of a support, and increasedby an amazing 112.3-122.3% by using both the support and the cesiumoxide. The following example shows that the substitution of sodium oxidefor cesium oxide in the process effects an even greater increase incatalytic activity but also increases the amount of methylpenteneby-product and the tar-like by-products obtained after methanolhydrolysis of the catalyst and reactor residues.

COMPARATIVE EXAMPLE D

Example I was essentially repeated except that 8.6 mmol of -325 meshsodium oxide was included in the initial charge to the reaction vesselinstead of the cesium oxide. The analytical results are shown below.

    ______________________________________                                        Time    Mols × 100                                                      (min.)  Toluene     IBB    NBB     MI   MP                                    ______________________________________                                         0      100         0      0       0    0                                      40     --          0.9    0.07    0    0.1                                    80     84.9        9.3    1.13    0.13 1.1                                   120     68.2        25.2   3.22    0.30 2.8                                   160     48.1        42.5   5.09    0.35 5.5                                   200     33.3        54.1   6.10    0.38 7.6                                   240     25.0        61.1   6.45    0.43 9.6                                   ______________________________________                                    

The amount of tar-like by-products obtained after methanol hydrolysis ofthe catalyst and reactor residues was determined to be 1.88 g/g of NaKand 3.13 g/mol of IBB formed.

It is obvious that many variations may be made in the products andprocesses set forth above without departing from the spirit and scope ofthis invention.

What is claimed is:
 1. In a process for coupling an alkene selected fromethene, propene, and mixtures thereof with an aromatic hydrocarbonhaving an active hydrogen on a saturated alpha-carbon in the presence ofa supported potassium or potassium alloy as a catalyst, the improvementwhich comprises conducting the reaction in the presence of cesium oxideas a co-catalyst, the catalyst composition containing about 200-1500weight % of support and about 4-40 mol % of co-catalyst, based on theamount of potassium or potassium alloy.
 2. The process of claim 1wherein the alkene is a mixture of propene and ethene.
 3. The process ofclaim 1 wherein the alkene is propene.
 4. The process of claim 1 whereinthe aromatic hydrocarbon is a hydrocarbon corresponding to the formulaRR'R"CH, in which R is an aryl group of up to 20 carbons and R' and R"are independently selected from hydrogen and alkyl and aryl groups of upto 20 carbons.
 5. The process of claim 4 wherein the aromatichydrocarbon is an alkylbenzene.
 6. The process of claim 5 wherein thealkylbenzene is toluene.
 7. The process of claim 1 wherein the supportedcatalyst is potassium.
 8. The process of claim 1 wherein the supportedcatalyst is a sodium-potassium alloy having a potassium content of40-90% by weight.
 9. The process of claim 1 which is conducted at atemperature of about 100°-300° C.
 10. The process of claim 9 wherein thereaction temperature is about 175°-200° C.
 11. The process of claim 1wherein the support is diatomaceous earth.
 12. The process of claim 1wherein the support is potassium carbonate.
 13. The process of claim 1wherein the support is alumina.
 14. The process of claim 1 whereinpropene is coupled with toluene at about 175°-200° C. in the presence ofa supported potassium or alloy catalyst and the co-catalyst.